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John Cartlidge: ALife XI, Winchester, UK8 5th August 2008 Couting Ones Watson & Pollack, GECCO 2001 Two populations of binary strings Goal: evolve as many 1s as possible Asymmetrical bias controlled by varying mutation bias of one population (parasites) When is it best to reduce virulence?

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John Cartlidge: ALife XI, Winchester, UK10 5th August 2008 Choosing RV Value Problem:  How do we know a priori what the asymmetry is likely to be?  Is asymmetry is likely to remain fixed? Solution:  Adapt virulence dynamically during runtime

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John Cartlidge: ALife XI, Winchester, UK15 5th August 2008 Lessons for epidemiology? Can we use DV for modelling virulence in natural systems? Can we translate ideas of RV to the natural world for control of infectious diseases?  Rather than attack parasites and encourage an arms-race, creating ‘super-bugs’, can we take a reduced virulence approach?  E.g.: ‘Scientists create GM mosquitoes to fight malaria and save thousands of lives’ (Guardian 2005) ‘Plan to breed and sterilize millions of male insects’ Project ‘almost ready for testing in wild’

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John Cartlidge: ALife XI, Winchester, UK16 5th August 2008 Summary / Conclusions Disengagement is problematic and is exacerbated by asymmetry Reducing virulence helps to promote engagement As asymmetry increases, virulence should fall Its hard to know a priori what virulence level to set DV is able to adapt virulence during evolution to find the best value DV has been shown to vastly outperform fixed virulence (and standard virulence) in the Counting Ones domain